Particle control screen assembly for a perforated pipe used in a well, a sand filter system and methods of making the same

ABSTRACT

A particle control screen assembly for a perforated pipe used in a well, a sand filter system, and methods of making same are provided. The screen assembly includes a woven mesh filter media disposed about the perforated pipe, and a protective wrapper disposed about the filter media. The protective wrapper comprises an outer perforated layer and an inner layer that is disposed between the outer layer and the filter media. A surface of the inner layer that faces the outer perforated layer has a non-smooth contour, with this surface of the inner layer having portions in direct contact with an inner surface of the outer layer. The inner layer is provided with apertures that are disposed in such a way that fluid cannot flow from the outer surface of the outer perforated layer directly radially both through holes of the outer layer and through the apertures of the inner layer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a new particle control screen assembly for aperforated pipe used in a well, to a sand filter system, and to methodsof making the same.

2. Prior Art Statement

It is known to provide a particle control screen assembly for aperforated pipe used in a well, the assembly including a woven meshfilter media means disposed about the perforated pipe, and a protectivewrapper means disposed about the filter media means. See the Padden U.S.Pat. No. 5,411,084; and the Whitebay et al, U.S. Pat. No. 5,232,048.

It is also known to provide a protective wrapper means that comprisestwo cylindrical, spaced-apart tubes that are each provided with holes.See Fast U.S. Pat. No. 4,064,938. The cylindrical walls of the tubes arevery thick for erosion control, and although the holes of the respectivecylindrical tubes are offset relative to one another, tangential flowthrough the holes of the outer tube allow relatively direct impingementof fluid from the outside against the filter media means. In addition,due to the thick walls and the spacing between them, this known wellscreen has a large outer diameter.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to overcome thedrawbacks of the heretofore known screen assemblies and to provide animproved screen assembly that prevents direct impingement of incomingfluid against the filter media means while at the same time minimizingthe overall size, and in particular the outer diameter, of such a screenassembly.

This object is realized pursuant to the inventive particle controlscreen assembly for a perforated pipe used in a well in that theprotective wrapper means comprises an outer perforated layer, and aninner layer that is disposed between the outer perforated layer and thefilter media means, the inner layer having a first surface that facesthe outer perforated layer and has a nonsmooth contour, said firstsurface of the inner layer having portions thereof in direct contactwith an inwardly facing surface of the outer perforated layer, and theinner layer being provided with apertures that are disposed in such away that fluid cannot flow from an outer surface of the outer perforatedlayer directly radially both through holes of said outer perforatedlayer and said apertures of said inner layer.

Accordingly, it is an object of this invention to provide a novelparticle control screen assembly having one or more of the novelfeatures of this invention as set forth above or hereinafter shown ordescribed.

Another object of this invention is to provide a new method of makingsuch a particle control screen assembly, the method of this inventionhaving one or more of the novel features of this invention as set forthabove or hereinafter shown or described.

Yet another object of this invention is to provide a new sand filtersystem comprising a particle control screen assembly disposed about aperforated pipe for use in a well, such a filter system having one ormore of the novel features of this invention as set forth above orhereinafter shown or described.

Other objects, uses and advantages of this invention are apparent from areading of the specification in conjunction with the accompanyingschematic drawings, which form a part thereof and wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially cross-sectioned view showing one exemplaryembodiment of the sand control screen assembly of this invention mountedon a base pipe in a well;

FIG. 2 is a cross-sectional view taken along the line 2--2 in FIG. 1;

FIG. 3 is a fragmentary, partially broken-away view of the two outerlayers of the inventive screen assembly taken in the direction of thearrows 3--3 in FIG. 2;

FIG. 4 is a partially cross-sectioned and partially broken-away viewshowing the various layers of the sand filter system of FIG. 1;

FIG. 5 is a view similar to that of FIG. 4 of a second exemplaryembodiment of the sand control screen assembly of this invention;

FIG. 6 is a cross-sectional view taken along the line 6--6 in FIG. 5;

FIG. 7 is a fragmentary, partially broken-away view of the two outerlayers of the inventive screen assembly taken in the direction of thearrows 7--7 in FIG. 6;

FIG. 8 is a partially cross-sectioned and partially broken away viewillustrating one manner for holding the layers of the inventive screenassembly in place relative to one another and for mounting such screenassembly on the base pipe;

FIG. 9 is an enlarged view of some of the weld locations of the screenassembly of FIG. 8; and

FIG. 10 is an enlarged view of an alternative weld means.

DESCRIPTION OF PREFERRED EMBODIMENTS

While the various features of this invention are hereinafter illustratedand described as providing a sand control screen assembly for aperforated pipe in an oil and/or gas producing well, it is to beunderstood that the various features of this invention can be utilizedsingly or in various combinations thereof to provide a sand or particlecontrol screen assembly for other systems and applications as desired.

Therefore, this invention is not to be limited to only the embodimentsillustrated in the drawings because the drawings are merely utilized toillustrate one of the wide variety of uses of this invention.

Referring now to the drawings, the improved sand or particle filtersystem of this invention is generally indicated by the reference numeral20 in the embodiment illustrated in FIGS. 1-4, and comprises a wellscreen or particle control screen assembly 21 that is mounted on a basepipe 22 that is disposed, for example, in the wellbore 23.

In order to be able to draw in, for example, petroleum or natural gasfrom the wellbore 23, a portion of the base pipe 22 is perforated by theholes 25. To prevent sand or other particles from being drawn into thebase pipe 22 through such holes 25, the perforated portion of the basepipe is covered by the particle control screen assembly 21. In theembodiment illustrated in FIGS. 1-4 (see also FIG. 8), the screenassembly 21 comprises a preferably multi-layer woven mesh filter mediameans 27 followed by a protective wrapper means 28. This protectivewrapper means comprises an inner perforated layer 29 and an outerperforated layer 30. The protective wrapper means 28 is spaced orseparated from the filter media means 27 by a gap 32 for a reason to bediscussed in detail subsequently.

As can be seen particularly clearly in FIGS. 3 and 8, the innerperforated layer 29 is provided with holes 34, while the outerperforated layer 30 is provided with holes 35. These holes 34, 35 areoffset from one another as viewed in a radial direction, again, for apurpose that will be discussed in greater detail subsequently.

A feature of the inventive screen assembly that, enhances the advantageachieved therewith can be seen in the particular configuration of theinner perforated layer 29. In particular, the surfaces 36 and 37 of theinner layer 29 are not smooth, being structured or profiled. And moreparticularly, especially the outer surface 36 of the inner layer 29 hasan embossed, i.e. a non-smooth, contour that is designated generally bythe reference numeral 38. However, due to the thinness of the innerlayer 29, an embossment of this layer will inherently result in anon-smooth contour on the inner surface 37 similar to the non-smoothcontour 38 of the outer surface 36 of the inner layer 29. To form theinventive sand filter system, an appropriate single or multi-layer wovenmesh filter media means 27 is disposed about the base pipe 22, and inparticular about the perforated portion 25 thereof. The nowcylindrically shaped filter media means 27 is secured to the base pipe22, for example by being welded thereto; representative weld locations40 are indicated in FIG. 1. The protective wrapper means 28, whichcomprises the inner perforated layer 29 and the outer perforated layer30, which can, for example, be welded together, similarly has acylindrical shape and can then be disposed about the filter media means27 to complete assembly of the sand filter system. To accomplish this,the inner diameter of the inner perforated layer 29 of the protectivewrapper means 28 has an inner diameter that is slightly greater than theouter diameter of the filter means 27 to allow the protective wrappermeans 28 to be slid over the filter media means 27 to complete assemblyof the sand filter system. In so doing, the gap 32 results between theinner perforated layer 29 and the filter media means 27. The protectivewrapper means 28 is then secured in position on the filter means 27, forexample by being welded thereto; representative weld locations areindicated by the reference numerals 41.

The operation of the inventive sand filter system is as follows. Afluid, such as crude oil or natural gas, is to be drawn through thefilter system, either by being pumped therethrough or due to thepressure existing in the borehole, to the earth's surface. In so doing,the fluid first passes through the radially directed holes 35 of theouter perforated layer 30. Since the holes 34 of the inner perforatedlayer 29 are offset axially and/or circumferentially from the holes 35of the outer perforated layer 30, the incoming fluid flow is inherentlydeflected or changes its flow direction and cannot continue to flowdirectly radially inwardly against the filter media means 27, which asexplained previously would result in rapid erosion of the filter mediameans. After the fluid passes through the holes 35 of the outerperforated layer 30, this fluid is deflected sideways by striking theouter surface 36 of the inner perforated layer 29. This deflection isenhanced by the embossed or non-smooth wavy contour 38 of the outersurface 36 of the inner perforated layer 29. The deflected fluid flowfinally reaches the holes 34 of the inner perforated layer 29 and canthen pass through the inner perforated layer to the filter media means27, which effects the actual filtration of the fluid for removal of sandand other particles therefrom so that the fluid can then pass throughthe holes 25 of the base pipe 22 and can then be drawn to the earth'ssurface.

In the embodiment of FIGS. 1-4 described above, radial flow through theprotective wrapper means 28 is deflected, to prevent damaging directradial flow against the filter means 27, by providing two perforatedlayers 29, 30 with the holes of the respective layers being offsetrelative to one another. However, it has also been found according tothe teachings of this invention that the inner layer of the protectivewrapper means can also have a configuration that is different from theconfiguration of the outer perforated layer of the protective wrappermeans and still be effective to divert the radial flow of fluid thatpasses through the holes of the outer perforated layer. For example,reference is now made to FIGS. 5-7, wherein another particle controlscreen assembly of this invention is generally indicated by thereference numeral 20A and parts thereof similar to the particle controlscreen assembly 20 of FIGS. 1-4 are indicated by like reference numeralsfollowed by the reference letter "A".

In the embodiment of FIGS. 5-7, the inner layer 29A of the protectivewrapper means 28A is in the form of a woven wire mesh layer 43 that isbonded to the outer perforated layer 30A. In a presently preferredembodiment of the control screen assembly 21A, the wire mesh layer 43comprises a twilled Dutch weave. The important feature of the mesh layer43 is that it comprises a very coarse weave of approximately 500 to 1000μm (in contrast to the filter media means 27, which is typically sizedin a range of less than 200 μm, depending upon the sand and particlesize). The mesh layer 43 is intended to act as a flow diffuser ratherthan as a filter. In particular, in such a weave, the fill wires areseparated by warp wires resulting in spaces and a wavy configuration, sothat again fluid that passes through the holes 35A of the outerperforated layer 30A is deflected by the wires of the mesh layer 43 toprevent direct radial flow of fluid through the holes 35A of the outerperforated layer 30A and against the filter media means 27A. Thedeflected fluid flow passes along the wires and then through the spacesof the mesh layer 43 and can then continue on to the filter media means27A for filtration of sand and other particles therefrom so that thefluid can then pass through the holes 25A of the base pipe 22A. The meshlayer 43 can have a thickness of, for example, 0.040-0.100 of an inch,preferably 0.055-0.059 of an inch.

As can be seen from FIG. 8, the screen assembly, be it 21 or 21A, can beassembled along the length of the base pipe in sections of a givenlength, for example, in four foot or nine foot sections, whereby eachsection is then secured to the base pipe such as being welded thereto.Furthermore, providing the screen assembly in sections providesstructural support for the screen assembly and also makes it possible tomaintain the gap 32 between the protective wrapper means 28 and thefilter media means 27. Various means for welding the components of theinventive control screen assembly to the base pipe and/or to one anotherare illustrated in FIGS. 8-10 by the weld locations 45, 46 and 47.Typical lengths for a base pipe are 20, 30 or 40 feet, although shorteror longer lengths are of course possible.

Reference has been made to the multi-layer woven mesh filter media means27, 27A. This filter media means is preferably a diffusion bonded orsintered wire mesh that is commercially available from PurolatorProducts Company, 8439 Triad Drive, Greensboro, N.C. and is sold underthe Registered Trademark "POROPLATE". The filter media means 27 ispreferably comprised of several layers of differing mesh size, forexample three layers as illustrated in FIGS. 4 and 5. It would also bepossible to dispose a larger mesh layer as a core wrap between thefilter media means 27 and the base pipe 22, for example in the situationwhere a two-layer filter media means is utilized. To provide greaterstructural support and to better span the holes 25 of the base pipe 22,a coarser weave or meshed layer of the multi-layer structure would beplaced closest to the base pipe 22. The filter media means 27 couldeither have a generally cylindrical configuration as shown in thedrawings, or could also be pleated in order to provide a greater surfacearea for filtration purposes. For example, see the aforementioned U.S.Pat. No. 5,411,084, Padden, whereby this U.S. Patent is beingincorporated into this disclosure by this reference thereto.

In a preferred embodiment of the present invention, all of the layersare made of metal, and in particular stainless steel. Furthermore, thelayers 29, 30 of the protective wrapper means 28 are relatively thin.For example, the inner perforated layer 29 can have a thickness of0.020-0.075 of an inch, and in one preferred embodiment has a thicknessof 0.025 of an inch, with the embossed depth providing a maximum gapbetween parts of the outer perforated layer 30 and the outer surface 36of the inner perforated layer 29 of from 0.040-0.125 of an inch. Thethickness of the outer perforated layer 30 can range from 0.060-0.130 ofan inch, and in one preferred embodiment has a thickness of 0.060 of aninch. The magnitude of the gap 32 between the filter media means 27 andthe protective wrapper means 28 is a minimum of 0.020 of an inch and canrange up to 0.125 of an inch or more, although it is advantageous tokeep the gap 32 as small as possible so that the overall outer diameterof the completed well screen assembly can be kept to a minimum.

Reference has also been made to the holes 34, 35 in the inner and outerperforated lengths 29, 30 respectively. The number, size and shape ofsuch holes can vary, with an optimum situation being achieved with amaximum open area that nonetheless does not allow any overlap of holesfrom the outer layer 30 to the inner layer 29 so that a direct orstraight through flow of fluid to the filter media means 27 is preventedas previously discussed.

While the forms and methods of this invention now preferred have beenillustrated and described as required by the Patent Statute, it is to beunderstood that other forms and method steps can be utilized and stillfall within the scope of the appended claim, wherein each claim setsforth what is believed to be known in each claim prior to this inventionin the portion of each claim that is disposed before the terms "theimprovement", and sets forth what is believed to be new in each claimaccording to this invention in the portion of each claim that isdisposed after the terms "the improvement", whereby it is believed thateach claim sets forth a novel, useful and unobvious invention within thepurview of the Patent Statute.

What is claimed is:
 1. In a particle control screen assembly for aperforated pipe used in a well, said assembly including a woven meshfilter media means disposed on one side of said perforated pipe, and aprotective wrapper means disposed adjacent said filter media meansremote from said pipe, the improvement wherein said protective wrappermeans comprises a first perforated layer, and a second layer that isdisposed between said perforated layer and said filter media means, saidsecond layer having a first surface that faces said perforated layer andhas a non-smooth contour, said first surface of said second layer havingportions thereof in direct contact with a facing surface of saidperforated layer, and said second layer being provided with aperturesthat are disposed in such a way that fluid cannot flow from an outersurface of said perforated layer directly radially both through holes ofsaid perforated layer and said apertures of said second layer.
 2. Ascreen assembly according to claim 1, wherein said woven mesh filtermedia means is disposed about said perforated pipe, and said protectivewrapper means is disposed about said filter media means, and whereinsaid protective wrapper means comprises a radially outer perforatedlayer, and as said second layer an inner layer that is disposed betweensaid outer perforated layer and said filter media means, said firstsurface of said inner layer having portions thereof in direct contactwith an inwardly facing surface of said outer perforated layer.
 3. Ascreen assembly according to claim 2, wherein said inner layer isembossed to effect said non-smooth contour of said first surfacethereof, whereby said first surface also has portions that are spacedfrom said inwardly facing surface of said outer perforated layer.
 4. Ascreen assembly according to claim 3, wherein said apertures of saidinner layer are holes.
 5. A screen assembly according to claim 4,wherein said holes of said inner layer are offset axially and/orcircumferentially relative to said holes of said outer perforated layer.6. A screen assembly according to claim 5, wherein some of said holes ofsaid inner layer are located closer to said inwardly facing surface ofsaid outer perforated layer than are other holes of said inner layer. 7.A screen assembly according to claim 3, wherein said inner layer isspaced from said filter media means.
 8. A screen assembly according toclaim 3, wherein said filter media means is a multi-layer woven andsintered together mesh.
 9. A screen assembly according to claim 3,wherein said filter media means, said inner layer, and said outerperforated layer are all made of metal.
 10. A screen assembly accordingto claim 9, wherein said inner layer is made of stainless steel having athickness of from 0.020-0.075 of an inch, and said outer perforatedlayer is made of stainless steel having a thickness of from 0.060-0.130of an inch.
 11. A screen assembly according to claim 7, wherein saidfilter media means, said inner layer, and said outer perforated layerall have an essentially cylindrical configuration.
 12. A screen assemblyaccording to claim 2, wherein said inner layer is a woven screen toeffect said non-smooth contour of said first surface thereof, wherebysaid first surface also has portions that are spaced from said inwardlyfacing surface of said outer perforated layer.
 13. A screen assemblyaccording to claim 12, wherein said woven screen comprises a twilledDutch weave.
 14. A screen assembly according to claim 13, wherein saidapertures of said woven screen are formed by wires of said weave beingseparated from one another by other wires thereof.
 15. A screen assemblyaccording to claim 12, wherein said woven screen is spaced from saidfilter media means.
 16. A screen assembly according to claim 12, whereinsaid filter media means is a multi-layer woven and sintered togethermesh.
 17. A screen assembly according to claim 12, wherein said filtermedia means, said woven screen, and said outer perforated layer are allmade of metal.
 18. A screen assembly according to claim 12, wherein saidwoven screen is secured to said outer perforated layer.
 19. A screenassembly according to claim 15, wherein said filter media means, saidwoven screen, and said outer perforated layer all have an essentiallycylindrical configuration.
 20. In a sand filter system comprising aparticle control screen assembly disposed about a perforated pipe foruse in a well, said assembly including a woven mesh filter media meansdisposed about said perforated pipe, and a protective wrapper meansdisposed about said filter media means, the improvement wherein saidprotective wrapper means comprises an outer perforated layer, and aninner layer that is disposed between said outer perforated layer andsaid filter media means, said inner layer having a first surface thatfaces said outer perforated layer and has a non-smooth contour, saidfirst surface of said inner layer having portions thereof in directcontact with an inwardly facing surface of said outer perforated layer,and said inner layer being provided with apertures that are disposed insuch a way that fluid cannot flow from an outer surface of said outerperforated layer directly radially both through holes of said outerperforated layer and said apertures of said inner layer.
 21. In a methodof making a particle control screen assembly for a perforated pipe usedin a well, said assembly including a woven mesh filter media meansdisposed about said perforated pipe, and a protective wrapper meansdisposed about said filter media means, the improvement comprising thestep of producing said protective wrapper means to comprise an outerperforated layer, and an inner layer that is disposed between said outerperforated layer and said filter media means, said inner layer having afirst surface that faces said outer perforated layer and has anon-smooth contour, said first surface of said inner layer havingportions thereof in direct contact with an inwardly facing surface ofsaid outer perforated layer, and said inner layer being provided withapertures that are disposed in such a way that fluid cannot flow from anouter surface of said outer perforated layer directly radially boththrough holes of said outer perforated layer and said apertures of saidinner layer.